1. Field of the Invention
The present invention relates to an infrared radiation detecting device for detecting infrared radiation. More specifically, the present invention relates to a thermopile-type infrared radiation detecting device having an infrared radiation absorbing unit on an upper surface of a central portion of a substrate and a thermopile formed on support beams.
2. Background Information
A conventional thermopile-type infrared radiation detecting device having an infrared radiation absorbing unit on an upper surface of a central portion of a substrate and a thermopile formed on a support beam is described in Japanese Laid-Open Patent Publication No. 2000-111396. The infrared radiation absorbing unit is supported over the substrate with a support beam that has been bent into an L shape to obtain a structure in which the infrared radiation absorbing unit and the substrate are thermally isolated from each other. The infrared radiation absorbing unit is configured and arranged to absorb infrared radiation and convert the infrared radiation into heat. An electromotive force or other output quantity resulting from the temperature difference between the light receiving unit (infrared radiation absorbing unit) and the substrate is extracted as a detection value by the thermopile.
In order to improve the sensitivity and the thermal insulation simultaneously, the thermopile of such infrared radiation detecting device is often made of p-type polycrystalline silicon and n-type polycrystalline silicon (hereinafter, polycrystalline silicon is referred as “polysilicon” or “poly-Si”). More specifically, in general, the number of thermocouples forming the thermopile is increased for the purpose of increasing the sensitivity of the infrared radiation detecting device and a plurality of conductors made of polysilicon, as mentioned above, or other material are often provided on a single support beam. For example, in the conventional infrared radiation detecting device described in the above mentioned publication, a thermopile including one pair of electrical conductors (i.e., the conductors made of p-type polycrystalline silicon and n-type polycrystalline silicon) is provided on the single support beam. In the conventional infrared radiation detecting device, the two electrical conductors are disposed parallel to each other.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved infrared radiation detecting device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.